Assessment of nitrates, nitrites, and selected heavy metal contaminants in the microgreens of rare oilseed plants.

Introduction: Microgreens are rich in health-promoting phytonutrients, although they can also be a source of contaminants. This study aimed to determine nitrates and nitrites as well as cadmium (Cd), arsenic (As), lead (Pb), and aluminium (Al) in the microgreens of three rare oilseed plants: nigella (Nigella sativa L.), camelina (Camelina sativa L.), and safflower (Carthamus tinctorius L.).

Methods: The plants were grown in the greenhouse of the Agricultural University of Krakow under strictly controlled conditions. The microgreens were cut with scissors when they had 1 true leaf. An AQ2 discrete analyzer was used to determine the concentrations of nitrites and nitrates. The Cd, As, and Pb levels were analyzed using ICP-MS/MS with a triple quadrupole spectrometer (iCAP TQ ICP-MS). The Al level was measured using the ICP-OES technique. Analyses were conducted in triplicate.

Results: In the tested microgreens, the amount of Cd fluctuated from 0.022 to 0.063 mg per 100 g dry matter (d.m.). The lowest statistically significant Cd level was found in the microgreens of nigella. The cadmium content in camelina and safflower did not differ significantly. The As content varied between 0.009 and 0.021 mg/100 g d.m., with nigella microgreens having the highest statistically significant As level. The statistically significantly highest levels of Pb, Al, and nitrates were found in the microgreens of camelina, with respective values of 0.071 mg, 13.81 mg, and 6131 mg/100 g d.m. No nitrites were detected in all analyses performed.

Conclusions: The examined species may be a source of contaminants and nitrates. In the present study, limits were not exceeded for Cd, As, Pb, Al, and nitrate levels, assuming a potential consumption of microgreens at 20 g per day based on TWI standards (Tolerable Weekly Intake) for Al and Cd, BMDL01- standards (Benchmark Dose Lower Confidence Limits) for Pb and As, as well as ADI-based standards (Acceptable Daily Intake) for nitrates.